1. Field of the Invention
The present invention relates to an image forming apparatus capable of duplex image formation by performing image formation on one side of a recording material first and then by performing image formation on the back side of the same recording material also by an electrophotographic process.
2. Description of the Related Art
Conventionally various kinds of image forming apparatus commonly including features like the following are proposed. The apparatus are equipped with a plurality of image forming portions adopting an electrophotographic process. Each image forming portion forms a toner image having a different color from each other. The toner images are sequentially superimposed on each other on the same recording material by being transferred to form a color image on the recording material. Furthermore, a color copying machine for performing color high-speed recording was proposed as an image forming apparatus. The machine is equipped with a transfer belt being a recording-material transporting member in a shape of an endless belt, and a plurality of image forming portions arranged in a straight line along the transfer belt.
A brief description of an example of the color copying machine is given on the basis of FIG. 1. In the machine, a first, a second, a third and a fourth image forming portions Pa, Pb, Pc and Pd are disposed. The image forming portions Pa, Pb, Pc and Pd are equipped with electrophotographic photosensitive drums 3 (3a, 3b, 3c, 3d) being respectively image bearing members for their respective exclusive use, and each color toner image is formed on each photosensitive drum 3. A transfer belt (recording material transportation member in the shape of a belt) 30 adjoining each photosensitive drum 3 is disposed. Each color toner image formed on each photosensitive drum 3 is superimposed on each other to be transformed on a recording material P to be transported by the transfer belt 30. After the recording material P, on which each color toner image is transferred, is heated and pressurized by a fixing device 9, the recording material P is delivered to the outside of the machine as a recording material P bearing a color recorded image.
In such an image forming apparatus, mold releasing oil (also called as xe2x80x9cfixing oilxe2x80x9d) such as dimethyl silicone oil is reserved in an oil reservoir 53 for the prevention of the adherence of the toner on a recording material to a fixing roller 51 of the fixing device 9, and the mold releasing oil is coated on the surface of the fixing roller 51 with a coating roller 50.
Moreover, because toner smear (mainly consisting of untransferred residual toner (called as xe2x80x9cfogging tonerxe2x80x9d) transferred from the photosensitive drums 3 to the transfer belt 30, and also including paper dust and the like as a part) exist on the transfer belt 30 that has finished transferring, the toner smear is scraped off by the abutting of a cleaning blade 8a that is made from an elastic material such as rubber and is fixed on a transfer belt cleaner 8 against the transfer belt 30, and the scraped toner is collected into the cleaner 8.
In the configuration shown in FIG. 1, the cleaning blade 8a is disposed such that the edge surface (a surface parallel to the thickness direction of the blade 8a from the abutting portion of the blade 8a against the transfer belt 30) of the blade 8a faces toward upward in the gravity direction.
Such a disposition of the cleaning blade 8a makes it easy to hold toner on the edge surface of the blade 8a, and the holding of the toner makes it possible to realize a stable slidableness at the abutting portion against the transfer belt 30, and also makes it possible to improve the cleaning performance partly owing to the addition of the polishing effect of the toner.
However, in the case where images are formed on two sides of a recording material in such an image forming apparatus, there is the possibility that toner excessively accumulates on the edge surface of the blade 8a to overflow upwards from the cleaner 8. The overflowed toner adheres to the back side of the recording material to become back side smear, or disperses in the apparatus to smear the inside of the apparatus.
The present inventor""s studies reveal the following cause of the accumulation of the toner on the edge surface of the blade 8a. That is, after images have been formed on one side of a recording material and then the formed images have been fixed by the fixing device 9, when the recording material is turned over and borne on the transfer belt 30 again for the image-forming on the back side (second side), the oil, which had been coated on the fixing roller 51 and was adhered to the front side (first side) of the recording material at the time of fixation, adheres to the transfer belt 30 to be carried to the cleaning blade 8a. Consequently, when the smear toner on the transfer belt 30 is carried to the blade 8a, the toner being powder is mixed with the oil to be clayey. The clayey toner accumulates on the edge surface of the blade 8a. 
Even if the image forming apparatus is one adopting the so-called intermediate transfer process in which toner images on a photosensitive drum is once transferred on an intermediate transfer member and then the images are transferred from the intermediate transfer member to a recording material, the aforesaid problem occurs when the cleaning device having the aforesaid configuration is used.
One object of the invention is to provide an image forming apparatus capable of preventing the overflow of toner owing to the excessive accumulation of the toner on a cleaning member for a recording material bearing member, intermediate transfer member or a transfer member, and capable of avoiding the troubles of the smearing in a machine, the back side smear of a recording material and the like.
For attaining the foregoing object, a preferable aspect of the invention comprises:
image forming means for forming a toner image;
a recording-material transporting member for bearing and transporting the recording material;
cleaning means equipped with a cleaning blade abutting against a surface of the recording-material transporting member; and
fixing means equipped with a fixing member on which a mold release agent is coated, the apparatus being capable of forming an image on a surface of the recording material, a fixing operation of which has been performed by the fixing means, the surface of the recording material being opposite to a surface thereof on which the toner image is transferred,
wherein:
the cleaning blade is arranged such that a normal line of a surface of the cleaning blade, which is close to an abutting portion against the recording-material transporting member and faces to an upstream side of a transportation direction of the recording-material transporting member against the abutting portion, is substantially directed to a gravity direction; and
the apparatus further comprises control means for controlling the apparatus to transfer a supply toner image, which is to be fed to the cleaning means, formed by the image forming means on the recording-material transporting member directly, and to feed the supply toner image transferred on the recording-material transporting member to the cleaning means by transporting the recording-material transporting member.
Another preferable aspect of the invention comprises:
image forming means for forming a toner image;
an intermediate transfer member for bearing the toner image formed by the image forming means;
transferring means for transferring the toner image borne on the intermediate transfer member onto a recording material;
cleaning means equipped with a cleaning blade abutting against a surface of the intermediate transfer member; and
fixing means equipped with a fixing member on which a mold release agent is coated, the apparatus being capable of forming an image on a surface of the recording material, a fixing operation of which has been performed by the fixing means, the surface of the recording material being opposite to a surface thereof on which the toner image is transferred,
wherein:
the cleaning blade is arranged such that a normal line of a surface of the cleaning blade, which is close to an abutting portion against the intermediate transfer member and faces to an upstream side of a transportation direction of the intermediate transfer member against the abutting portion, is substantially directed to a gravity direction; and
the apparatus further comprises control means for controlling the apparatus to bear a supply toner image, which is to be fed to the cleaning means, formed by the image forming means on the intermediate transfer member, and to feed the supply toner image borne by the intermediate transfer member to the cleaning means by transporting the intermediate transfer member.
A further preferable aspect of the invention comprises:
image forming means for forming a toner image;
a transfer member for transferring the toner image formed by the image forming means onto a recording material;
cleaning means equipped with a cleaning blade abutting against a surface of the recording-material transporting member; and
fixing means equipped with a fixing member on which a mold release agent is coated, the apparatus being capable of forming an image on a surface of the recording material, a fixing operation of which has been performed by the fixing means, the surface of the recording material being opposite to a surface thereof on which the toner image is transferred,
wherein:
the cleaning blade is arranged such that a normal line of a surface of the cleaning blade, which is close to an abutting portion against the transfer member and faces to an upstream side of a transportation direction of the transfer member against the abutting portion, is substantially directed to a gravity direction; and
the apparatus further comprises control means for controlling the apparatus to transfer a supply toner image, which is to be fed to the cleaning means, formed by the image forming means on the transfer member directly, and to feed the toner image to the cleaning means by transporting the transfer member.
According to the present invention, toner images are directly formed periodically on a recording-material transporting member of recording materials, an intermediate transfer member or a transfer member in an image forming apparatus capable of two-side printing, and then the toner is fed to the cleaning blade of the recording-material transporting member of the recording materials, the cleaning blade of the intermediate transfer member or the cleaning blade of the transfer member. Consequently, the accumulation of toner on those cleaning blades, which accumulation is caused by the movement of oil adhered to the recording materials at the time of fixing to the recording-material transporting member, the intermediate transfer member or the transfer member, can be prevented. Thereby, the occurrence of the problems such as the smearing in the machine, the back side smear of the recording materials, and the like can be prevented.